1. Field
A magnetron for a microwave oven is disclosed herein.
2. Background
Generally, the magnetron is a device which is mounted in a microwave oven, or an illumination device, for example, and converts electric energy into high-frequency energy, such as microwaves. The magnetron can be divided into an anode, a cathode, or a magnetic portion, for example, in terms of operation.
A structure of the magnetron is disclosed in Korean Patent Laid-Open Publication No. 10-2002-0037078, published on May 18, 2002 and hereby incorporated by reference, which is the related art. In an operation of the related art magnetron for a microwave oven, a magnetic field formed by the permanent magnets forms a magnetic circuit along an upper magnetic pole and a lower magnetic pole, so that a magnetic field is generated in a working space between a vane and a filament. The filament emits thermal electrons at a temperature of about 2000K while an external power is applied to the filament. In the working space, an electron group is formed by the emitted thermal electron. The electron group is rotated within the working space by an anode voltage of 4.0 to 4.4 kV and a magnetic field which is applied between the filament and the anode portion.
More specifically, a strong electric field is formed in the working space by the anode voltage applied to the anode and the magnetic field acts in a vertical direction of the electric field. By the electric field and the magnetic field, the electron group proceeds to the vane while performing a cycloid movement in the working space and a high frequency having a resonance frequency corresponding to the speed at which the electron group rotates is induced to the vane. In other words, the magnetron generates microwaves of 2.45 GHz by being applied a high-voltage power to radiate the microwaves to a cooking chamber of the microwave oven, and the microwave cooks food in the cooking chamber.
The frequency band of 2.4 to 2.5 GHz is an industrial scientific medical (ISM) band, which is a band that industrial, scientific, and medical devices can use without authorization or restrictions. Not only microwave ovens but also household appliances, such as Bluetooth, WI-FI, and a television use the ISM band.
As many electronic devices can use the ISM band without limitation, unnecessary noise generated in any electronic device may cause a malfunction in the operation of other electronic devices. In other words, electromagnetic interference (EMI) may be generated. Therefore, in order to prevent the electromagnetic interference, the noise generated during the operation of the electronic device must be decreased.
On the other hand, the magnetron for the microwave oven generates not only electromagnetic waves in the ISM band, but also electromagnetic waves in a frequency band other than the ISM band. A prevention standard of the electromagnetic interference (EMI) is 92 dB μV/m (hereinafter, the unit thereof is simply referred to as “dB”) in the frequency range of 2.5 GHz to 5.725 GHz, and in a case where the microwave oven product has a peak value which is less than 88 dB (a value of 92 dB-4 dB) in the corresponding frequency range, it can be determined that the prevention standard described above is met. In the case of the related art magnetron for a microwave oven, the peak value in the frequency range of 2.5 GHz to 2.6 GHz has a value level slightly lower than 92 dB, and thus, there is a problem of exceeding the standard in a case in which an unexpected problem is generated during operation of the microwave oven.